The present invention relates generally to automated circuitry for detecting and locating faults in electrical transmission lines. It comprises electronic circuits at both a master unit and a remote unit linked to one another through conventional communication facilities.
This disclosure relates to a unique system for synchronizing operation of a remote and master unit, and for facilitating transfer of information between them through a conventional communication line. It eliminates the need for more expensive specialized communication facilities required by systems that preceded it.
An earlier automatic fault locating system is described in IEEE conference paper C 72 513-0, titled "Automatic Fault Locator for Bonneville Power Administration" by Marihart and Haagenson, printed in 1972. The described system initiates a start pulse when the fault is detected at the master unit. A signal from the remote terminal is transmitted by microwave to the master unit as a stop pulse. The time between pulses is interpreted in units of miles from the fault to the remote terminal. The paper discusses input filter requirements and details of the circuitry.
Another article summarizing methods for fault detection is AIEE paper 57-160, titled "Fault Location MEthods for Overhead Line" by Stringfield, Marihart, and Stevens. It discusses development of timing signal and time interval counters prior to currently available microprocessor technology. A system is discussed as "Type D" beginning at the bottom of page 525, where surges travel toward opposite ends of a line, are detected upon arrival and are made to stop synchronized electronic counters at the two ends. The readings at the two ends are then determined by separate operators, who can telephone the readings to a dispatcher. The article discusses the problem of triggering the equipment by unwanted pulses, such as noise, lightning near misses, and surges from other parts of the system, which would then disable the device until it is manually reset.
A digital fault location system is described in U.S. Pat. No. 4,107,778, issued Aug. 15, 1978. It utilizes a digital computer which detects the occurrence of a fault in the power transmission line and calculates the distance from the detection point to the fault. Voltage and current information is received through electric communication lines to arrive at distance calculations.